No. W3Schools is nowhere close to being 99% accurate. They refuse to correct blatant, longstanding errors. They refuse to make clear that they are not affiliated with the W3C. They repeatedly encourage very poor practices.
Moreover, the site in question, at its very top, suggests some very clear improvements to W3Schools, the most obvious and effective being to convert it into a wiki that will allow for self-correction and keeping the content up-to-date.
They also detail how there have been numerous attempts at building alternatives, but W3Schools retains too much unwarranted Google juice for those alternatives to be viable.
Moreover, the site in question, at its very top, suggests some very clear improvements to W3Schools, the most obvious and effective being to convert it into a wiki that will allow for self-correction and keeping the content up-to-date.
They also detail how there have been numerous attempts at building alternatives, but W3Schools retains too much unwarranted Google juice for those alternatives to be viable.